Remaining change will be sent back to the sending bitcoin address (source address). Simple.

The amount of bitcoins you can spend will be checked before sending. Use the view history button for details.
If the address has transactions pending with 0 confirmations, you will have to wait to send funds. 1 confirmation is
enough to send bitcoins.

You can set the miner transaction fee to any value you choose. or 0.

Advanced Split Wallet You can create a private key with 3 components.
Send the 3 components to 3 friends.
And 2 friends are required to create an usable private key to spend the
bitcoins.

If you don't have the private key, you don't own Bitcoin.
Be your own bank
Design Objective.

Offline Bitcoin Transaction

An offline Bitcoin transaction is created with a computer that is not connected to the internet (or any network).
Offline Transactions are also called Air-Gapped.
Assuming the installation process was secure the computer can not be reached by hackers.
Offline Howto